The hinge‐bending mode of a lysozyme–inhibitor complex

The hinge‐bending mode of hen egg white lysozyme is studied by a constrained minimization technique. Results with and without a bound inhibitor, tri‐N‐acetyl‐glucosamine, are obtained. The frequency of the mode with the inhibitor is found to be 4.3 cm−1, in contrast to 3.0 cm−1 for the free enzyme. Also, the hinge‐bending angle with the lowest energy is shifted 10° towards a more closed cleft in the bound species. The main contribution to these differences arise from interactions with the residues lining the cleft and those on the back side of it. Structural details that account for the energetics are presented. The method of calculation is somewhat different from a previous study [J. A. McCammon, B. R. Gelin, M. Karplus & P. G. Wolynes, (1976) Nature 262, 325–326] to reduce the likelihood of artifacts in the results.